1. Field of the Invention
This invention relates to a method of making a light guide member composed of a thermoplastic material for light transmission and having one linear end portion and one approximately cylindrical end portion. This invention particularly relates to a method of making a light guide member composed of a thermoplastic material which involves a high level of residual internal stress due to plastic deformation.
2. Description of the Prior Art
Light guide members having a linear portion at one end and an approximately cylindrical portion at the other end are used, for example, for accurately detecting light emitted from stimulable phosphors upon stimulation thereof in a radiation image recording and reproducing apparatus. In the radiation image recording and reproducing apparatus, a stimulable phosphor is exposed to a radiation passing through an object to have a radiation image stored therein, and then scanned with stimulating rays which cause the stimulable phosphor to emit light in proportion to the radiation energy stored. The emitted light is detected and converted into an electric image signal, and a visible image is reproduced by use of the obtained electric image signal.
After the electric image signal is obtained by photoelectrically detecting the light emitted from the stimulable phosphor upon stimulation thereof, signal processings such as gradation processing and frequency processing are conducted on the electric image signal to obtain a visible radiation image having a desired quality. This step can be achieved relatively easily. However, if the light emitted from the stimulable phosphor upon stimulation thereof is not detected sufficiently or uniformly in the readout step, the electric image signal obtained thereby becomes insufficient or non-uniform. Thus it is not always possible to obtain a correct, uniform visible radiation image. Therefore, in the read-out apparatus, it is desired to use a light guide member which sufficiently collects the light emitted from the stimulable phosphor upon stimulation thereof and which exhibits an equal light collecting efficiency over the entire surface of the sheet comprising the stimulable phosphor scanned with stimulating rays such as laser beams.